Joan Aiken 
Go Saddle The Sea [EPUB ebook] 

Despised by his Spanish relatives and ignored by his distant grandfather, twelve-year-old orphan Felix Brooke is lonely and unhappy. So when he’s given a parcel with a blood-stained letter from his dead father, it inspires him to track down his long-lost English family. Felix packs his bag, jumps on his trusty mule and heads for the coast and a new life. But his journey across the mountains and over the sea does not prove to be plain sailing — as Felix soon discovers . . .